The present invention relates to a low-temperature testing device which is used for testing the temperature characteristics of specimens of, for example, superconducting materials, and particularly to a low-temperature testing device in which specimens can be easily changed and the temperatures of specimens can be arbitrarily controlled.
Recently, competition in development of superconducting materials has become progressively keener, and it is extremely important to test the characteristics such as the critical temperature of a newly developed material. Examples of devices that are generally used in the measurement of the critical temperature of a new material include a device in which a sample-receiving chamber provided adjacent to a cooling portion of a Grifford-McMahon refrigeration unit or an improved type thereof is received in an adiabatic vacuum vessel so that a specimen received in the chamber can be cooled by heat transfer through a gas or a solid and a device in which a vessel receiving liquid helium or liquid nitrogen and a sample-receiving chamber placed adjacent to the bottom of the vessel are provided in an adiabatic chamber typically having a vacuum layer so that a specimen placed in the sample-receiving chamber can be cooled by heat transfer to liquid helium or liquid nitrogen.
However, each time the specimen is changed, adiabatic vacuum in these conventional low-temperature testing devices must be broken, and the operation of the refrigeration machine in the former device must be stopped. Therefore, the conventional devices each have a disadvantage in that the low-temperature atmosphere in the sample-receiving chamber of each of the devices which is achieved by the preceding test cannot be retained for the next test, and the temperature of the sample-receiving chamber thus returns to room temperature each time the specimen is changed. Each of the conventional low-temperature testing devices also have a disadvantage in that the temperatures of the sample-receiving chamber and the specimen are not easily raised or lowered at a controlled rate and a wide range.
Therefore, it is an object of the present invention to provide a temperature testing device which is provided with a sample-receiving chamber in which a specimen can be changed without adiabatic vacuum being broken, and which can be always maintained at a low temperature.
It is another object of the present invention to provide a low-temperature testing device in which the temperature of a sample-receiving chamber and a specimen can be precisely and easily controlled over a wide range by cooling the sample-receiving chamber with a circulating gaseous refrigerant.
Other objects of the present invention will be made clear from the description below.